Purpose: Denervation of the carotid sinus causes baroreflex and chemoreflex failure, resulting in labile hypertension and loss of hypoxic responsiveness. We investigated whether radiation therapy for laryngeal or pharyngeal cancer affects baroreflex and chemoreflex function.
Methods and materials: Twelve patients were studied after radiation therapy for locally advanced laryngeal or pharyngeal cancer (11 male, 1 female, age: 56.0 +/- 7.9 years), 3.3 years (median; range 1.0-4.7) after radiotherapy and 15 healthy controls (11 male, 4 female, 53.4 +/- 9.2 years). We measured baroreflex sensitivity (phenylephrine), blood pressure level and variability (24-h Spacelabs and 5-h Portapres recordings), responses to cardiovascular reflex tests, and the ventilatory responses to normocapnic and hypercapnic hypoxia.
Results: Baroreflex sensitivity was lower in patients (9.7 +/- 7.8 ms/mm Hg) than in controls (17.5 +/- 10.3 ms/mm Hg, p = 0.011). Mean office blood pressure was significantly higher in patients (141.5 +/- 27.8/89.2 +/- 10.6 mm Hg, 63.3 +/- 12.3 bpm) than in controls (117.3 +/- 10.1/75.1 +/- 6.8 mm Hg, 61.8 +/- 10.8 bpm). Blood pressure variability was not different between groups, nor were the responses to reflex tests. The normo/hypercapnic ventilatory response to hypoxia was similar in patients (0.21 +/- 0.10/1.37 +/- 0.60 L/min/%) and controls (0.22 +/- 0.16/1.19 +/- 0.78 L/min/%).
Conclusions: Radiation therapy for laryngeal or pharyngeal carcinoma does not affect chemoreflex function, but results in an attenuated baroreflex sensitivity. Clinically relevant blood pressure lability is absent however.